Electrochemical additive manufacturing method using deposition feedback control

ABSTRACT

A system and method of using electrochemical additive manufacturing to add interconnection features, such as wafer bumps or pillars, or similar structures like heatsinks, to a plate such as a silicon wafer. The plate may be coupled to a cathode, and material for the features may be deposited onto the plate by transmitting current from an anode array through an electrolyte to the cathode. Position actuators and sensors may control the position and orientation of the plate and the anode array to place features in precise positions. Use of electrochemical additive manufacturing may enable construction of features that cannot be created using current photoresist-based methods. For example, pillars may be taller and more closely spaced, with heights of 200 μm or more, diameters of 10 μm or below, and inter-pillar spacing below 20 μm. Features may also extend horizontally instead of only vertically, enabling routing of interconnections to desired locations.

This patent application is a continuation of U.S. patent applicationSer. No. 17/112,909, filed 4 Dec. 2020, which is a continuation-in-partof U.S. patent application Ser. No. 16/941,372, filed 28 Jul. 2020,which claims benefit of U.S. Provisional Patent Application Ser. No.62/983,274, filed 28 Feb. 2020 and U.S. Provisional Patent ApplicationSer. No. 62/890,815, filed 23 Aug. 2019, the specifications of which arehereby incorporated herein by reference. U.S. patent application Ser.No. 17/112,909 claims benefit of U.S. Provisional Patent ApplicationSer. No. 63/069,203, filed 24 Aug. 2020.

BACKGROUND OF THE INVENTION

One or more embodiments of the invention are related to the fields ofelectronics and 3D printing. More particularly, but not by way oflimitation, one or more embodiments of the invention enable a system andmethod of adding interconnection features to a plate usingelectrochemical additive manufacturing.

Additive manufacturing, also known as 3D Printing, is often used for theproduction of complex structural and functional parts via alayer-by-layer process, directly from CAD (computer aided drafting)models. Additive manufacturing processes are considered additive becausematerials are selectively deposited on a substrate to construct theproduct. Additive manufacturing processes are also typically layeredmeaning that layers of the product to be produced are fabricatedsequentially.

Currently, widespread use of metal additive manufacturing techniques islimited due to the high cost associated with selective laser melting(SLM) and electron beam melting (EBM) systems. Further, most metaladditive manufacturing devices currently in the industry use powderedmetals which are thermally fused together to produce a part, but due tomost metals' high thermal conductivity this approach leaves a roughsurface finish because unmelted metal powder is often sintered to theouter edges of the finished product.

An emerging alternative for additive metal manufacturing is to useelectrochemical reactions. In an electrochemical manufacturing process,a metal part is constructed by plating charged metal ions onto a surfacein an electrolyte solution. This technique relies on placing adeposition anode physically close to a substrate in the presence of adeposition solution (the electrolyte), and energizing the anode causingcharge to flow through the anode. This creates an electrochemicalreduction reaction to occur at the substrate near the anode anddeposition of material on the substrate. An illustrative apparatus thatenables additive manufacturing via electroplating is described forexample in U.S. Utility Pat. No. 10,465,307, “Apparatus forElectrochemical Additive Manufacturing,” by the inventors of the instantapplication. This apparatus demonstrated a novel approach toelectrochemical additive manufacturing that uses a printhead with anarray of anodes to build portions of each layer of a part in parallel,instead of moving a single anode across a part to sequentially constructportions of the layer.

BRIEF SUMMARY OF THE INVENTION

Additive manufacturing processes known in the art typically add materialin pre-programmed patterns. For example, material may be emitted from aprinthead for a preprogrammed period of time at a preprogrammed rate toconstruct a layer of a part. In electrochemical manufacturing, the rateand pattern of material deposition depends on many dynamic factors, suchas the distance between the printhead and each location of the part, thelocal density of metal ions in the electrolyte, and electrolyte flowpatterns. As a result, it is difficult or impossible to achieve highquality parts using strictly preprogrammed (“open loop”) control.However, feedback control methods for electrochemical additivemanufacturing processes are not well-developed.

One or more embodiments described in the specification are related to anelectrochemical additive manufacturing method using deposition feedbackcontrol. An object to be manufactured may be constructed by placing acathode and an anode array into an electrolyte solution. Depositionanodes of the anode array may provide current that flows from the anodeto the cathode through the electrolyte solution, resulting in depositionof the material onto the cathode. The manufacturing process may use abuild plan with a layer description for multiple layers of the object;each layer description may include a target map, which describes thepresence or absence of material at locations within the layer, and oneor more process parameters that affect the layer build. Manufacturing ofa layer may begin by setting or confirming the position of the cathoderelative to the anode array. Then control signals may be sent to theanode array based on the layer description. One or more feedback signalsmay be measured across the anode array, and these signals may beanalyzed to generate a deposition analysis that indicates the extent towhich deposition has progressed at locations within the layer. Thedeposition analysis may be used to determine whether the layer iscomplete, and to modify the process parameters associated with thelayer. When a layer is complete, manufacturing may continue for asubsequent layer.

In one or more embodiments, the layer description of one or more layersmay be modified before manufacturing the layers. For example, layerdensities may be changed.

Analysis of feedback signals may apply one or more transformations tothese signals, such as morphological filters or Boolean operators.

Feedback signals may for example include a map of current across theanode array. The deposition analysis may be generated by applying athresholding operation to this current map.

Determining whether a layer is complete may for example includecomparing the number of actual deposited pixels to the number of desireddeposited pixels within the layer. In one or more embodiments, a layermay be complete when the ratio of actual to desired deposited pixelsreaches or exceeds a threshold value. In one or more embodiments, alayer may be complete when a desired fraction of the desired depositedpixels are within a threshold distance from an actual deposited pixel.In one or more embodiments, the layer may be divided into components,and completion tests may be applied to each component; a layer may beconsidered complete when all components are complete. For example, acomponent may be complete when the ratio of actual to desired depositedpixels within the component reaches or exceeds a threshold value, orwhen a desired fraction of the desired deposited pixels within thecomponent are within a threshold distance from an actual depositedpixel.

In one or more embodiments, a layer description may includeidentification of whether a layer has an overhang. Manufacturing of alayer with an overhang may include successively depositing portions ofthe overhang so that they extend laterally from one or more previouslydeposited portions.

In one or more embodiments, a layer target map may be divided intoregions, and construction of the layer may include alternatelyactivating deposition anodes associated with each region.

In one or more embodiments, manufacturing of a layer may includecalculating a map of desired current output from each deposition anode,so that this current output will generate deposition corresponding tothe layer's target map. This current map calculation may involveapplying one or more transformations to the layer target map.

In one or more embodiments, modification of process parametersassociated with a layer may include calculation of voltage, current, ortime of activation for one or more deposition anodes.

In one or more embodiments, setting or confirming the position of thecathode relative to the anode may include obtaining sensor signals thatvary based on this relative position, such as a current value or avoltage value.

In one or more embodiments, manufacturing of a layer may include one ormore maintenance actions that maintain the condition of the anode arrayor the electrolyte solution. For example, these maintenance actions mayreplace material onto one or more deposition anodes that have eroded.Maintenance actions may activate one or more deposition anodes to removea film that has formed. Maintenance actions may include removal ofbubbles from the electrolyte solution.

In one or more embodiments, electrochemical additive manufacturing maybe used to manufacture one or more interconnection features, such aswafer bumps or pillars, for example. A plate, such as for example asilicon wafer or other substrate, may have one or more tiles, each ofwhich has one or more connection points. The plate may have a conductiveseed layer. To construct interconnection features that are electricallycoupled to these connection points, the conductive seed layer may becoupled to a power supply, placed into contact with an electrolyte, andaligned with an anode array; the current flowing from each depositionanode of the anode array may be controlled to deposit material onto theplate in the desired locations, forming the desired interconnectionfeatures.

Aligning the plate and the anode array may use one or more sensors todetermine the three-dimensional position and three-dimensionalorientation of the plate relative to the anode array, and using one ormore actuators to modify this three-dimensional position andthree-dimensional orientation of the plate relative to the anode array.

In one or more embodiments, after depositing material, portions of theconductive seed layer not covered by interconnection features may beremoved. In one or more embodiments, the initial conductive seed layermay be thickened using electrodeposition.

In one or more embodiments, some or all of the interconnection featuresmay have portions that are not substantially perpendicular to the plate;for example, they may extend horizontally. These portions may beconstructed by successively activating horizontally offset anodes togrow the deposit horizontally. In one or more embodiments, a verticalportion of one or more features may be deposited, followed by depositionof an inert material onto the plate to provide support for subsequenthorizontal portions. In one or more embodiments, non-perpendicularfeatures may be constructed by rotating the plate so that the previouslyconstructed vertical segments become horizontal, and depositing thesubsequent portions vertically.

In one or more embodiments, the anode array may be successively placedin position near different sets of tiles to construct interconnectionfeatures for each tile.

One or more embodiments of the invention may include an electrochemicaladditive manufacturing system, which may be used for example to createinterconnection features. The system may have a reaction chamber thatcontains an ionic solution that can be decomposed by electrolysis. Itmay have an anode array disposed in the reaction chamber and configuredto be immersed in the ionic solution. It may have a substrate disposedin the reaction chamber, where a conductive seed layer on a surface ofthe substrate is configured to be in contact with the ionic solution. Itmay have a mechanical positioning system that is configured to modifyone or more of the position and orientation of one or both of the anodearray and the substrate. It may have a microcontroller that isprogrammed to transmit control signals to the mechanical positioningsystem to modify the relative position and orientation of the anodearray and the substrate so that the anode array and the substrate aresubstantially coplanar, and the anode array is aligned with one or morefeatures of the substrate. The microcontroller may also accept athree-dimensional model of interconnection features to be added to thesubstrate. Based on this model, the microcontroller may control thecurrent through each anode of the anode array to construct theinterconnection features on the substrate.

One or more embodiments of the electrochemical additive manufacturingsystem may include one or more attachments that are configured toprovide an electrical connection to the conductive seed layer.

In one or more embodiments of the electrochemical additive manufacturingsystem, the substrate may have two or more tiles. The microcontrollermay successively position the anode array relative to the substrate tostep through the tiles. For example, it may transmit a first set ofcontrol signals to the mechanical positioning system to align the anodearray with a first tile of the two or more tiles, and then control thecurrent through each anode of the anode array to construct theinterconnection features on the first tile. Afterwards it may transmit asecond set of control signals to the mechanical positioning system toalign the anode array with a second tile of the two or more tiles, andthen control the current through each anode of the anode array toconstruct the interconnection features on the second tile.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the inventionwill be more apparent from the following more particular descriptionthereof, presented in conjunction with the following drawings wherein:

FIG. 1 shows a flowchart of an embodiment of the invention thatsuccessively manufactures layers using feedback control to assess layercompletion and to adjust parameters during manufacturing.

FIG. 2 shows an architectural block diagram of illustrativeelectrodeposition equipment that may be used to implement one or moreembodiments of the invention.

FIG. 3 shows an illustrative build plan for layers of an object, withtarget maps for each layer showing desired areas of deposited material,and process parameters describing how the layer is to be manufactured.

FIG. 4 illustrates density manipulation to generate a porous base layerthat facilitates part removal.

FIG. 5 illustrates detection of an overhang in a layer.

FIG. 6 illustrates manufacturing steps for the overhang detected in FIG.5 .

FIG. 7 shows an illustrative embodiment of feedback using currentsensors across the anode array.

FIG. 8 shows an illustrative map of current sensor feedback signals, andprocessing of these signals to form a map of deposition areas within alayer.

FIG. 9A shows an illustrative method to test for layer completion basedon the current sensor data of FIG. 8 .

FIG. 9B shows an extension of the layer completion test of FIG. 9A,which tests separately for completion of all connected components of thelayer.

FIG. 10 illustrates update of anode outputs based on the current sensorfeedback signals of FIG. 8 .

FIGS. 11A, 11B, and 11C illustrate a potentially complex relationshipbetween anode currents and deposited material, which may requirepre-processing to obtain the desired deposition pattern.

FIG. 12A illustrates calculation of anode currents to obtain a desireddeposition pattern.

FIG. 12B shows an illustrative two-dimensional example of calculating apattern of anode currents to obtain a desired deposition pattern.

FIG. 13 shows an illustrative embodiment that alternates anode outputacross different regions.

FIG. 14 shows illustrative maintenance actions that may be performedduring layer manufacturing to address issues in the anode array or theelectrolyte.

FIG. 15 shows an illustrative part manufactured using an embodiment ofthe invention.

FIG. 16 shows an illustrative application of an embodiment of theinvention, which adds wafer bumps to a wafer by depositing the bumpsusing electrochemical additive manufacturing.

FIG. 17 shows an illustrative flowchart of a method for adding waferbumps or similar features to a plate using electrochemical additivemanufacturing.

FIG. 18 shows illustrative equipment that may be used to implement themethod shown in FIG. 17 .

FIG. 19 shows illustrative steps in a process to add interconnectionfeatures to a plate, which builds these features on top of a seed layerthat is then removed.

FIG. 20A shows an illustrative profile of wafer bumps. FIG. 20B shows anillustrative profile of taller and denser features that may be addedusing an embodiment of the invention. FIG. 20C shows illustrativefeatures with horizontal sections that may be generated using anembodiment of the invention.

FIG. 21 shows illustrative steps that may be used in one or moreembodiments to construct horizontal features such as those shown in FIG.20C.

FIGS. 22A, 22B, and 22C illustrate different types of electrodeconfigurations that may be used in one or more embodiments: FIG. 22Aillustrates non-independent electrodes, non-independently controlled;FIG. 22B illustrates independent electrodes, non-independentlycontrolled; and FIG. 22C illustrates independent electrodes,independently controlled.

DETAILED DESCRIPTION OF THE INVENTION

A system and method of adding interconnection features to a plate usingelectrochemical additive manufacturing will now be described. One ormore embodiments of the invention may enable manufacturing of objects bypassing electrical current through an electrolyte to deposit materialonto the object, and by monitoring feedback signals during deposition toadjust manufacturing process parameters throughout the process. In oneor more embodiments, the object to be manufactured may be for example aplate, such as a silicon wafer, to which interconnection features (suchas wafer bumps) may be added. In the following exemplary description,numerous specific details are set forth in order to provide a morethorough understanding of embodiments of the invention. It will beapparent, however, to an artisan of ordinary skill that embodiments ofthe invention may be practiced without incorporating all aspects of thespecific details described herein. In other instances, specificfeatures, quantities, or measurements well known to those of ordinaryskill in the art have not been described in detail so as not to obscurethe invention. Readers should note that although examples of theinvention are set forth herein, the claims, and the full scope of anyequivalents, are what define the metes and bounds of the invention.

In an electrochemical additive manufacturing process, a metal part isconstructed by reducing charged metal ions onto a surface in anelectrolyte solution. This technique relies on placing a depositionanode physically close to a substrate in the presence of a depositionsolution (the electrolyte), and energizing the anode causing charge toflow through the anode. This creates an electrochemical reductionreaction to occur at the substrate near the anode and deposition ofmaterial on the substrate. A particular challenge of electrochemicalmanufacturing is that the rate and quality of deposition of material maybe highly variable, and may vary across time and across locations basedon multiple factors such as current density, electrolyte composition,fluid flows within the electrolyte, and distances between anodes andpreviously deposited material. For this reason, the inventors havediscovered that an important factor in constructing high-quality partswith electrochemical additive manufacturing is to employ a “closed loop”feedback control system that monitors deposition throughout themanufacturing process, and that adjusts manufacturing parametersaccordingly. This approach contrasts with a typical “open loop” additivemanufacturing process used by most 3D printers, for example, wherelayers are constructed successively based on pre-programmed commands.

FIG. 1 shows illustrative steps for an electrochemical additivemanufacturing process that incorporates deposition feedback control.These steps are illustrative; one or more embodiments may use differentor additional steps and may perform operations in different orders. Themanufacturing process illustrated in FIG. 1 has a planning phase 100,and a building phase 120. In the planning phase 100, a model 101 of anobject is analyzed by planning step or steps 102 to generate a buildplan 103 for construction of the object. The planning step or steps 102may execute on any processor or processors, such as for example, withoutlimitation, a computer, a microprocessor, a microcontroller, a desktop,a laptop, a notebook, a server, a mobile device, a tablet, or a networkof any of these processors. In one or more embodiments, the planningstep (or steps) 102 may for example slice a 3D object model 101 intolayers, and develop a plan to construct each layer. The build plan 103may include a layer description for each layer; a layer description mayinclude for example a target map for the layer and various processparameter values for construction of the layer. The target map mayinclude a two-dimensional grid or image showing locations within thelayer where material is to be deposited. The process parameters for alayer may include any variables that affect the physical or electricalprocesses that construct the layer; these parameters may include forexample, without limitation, current density range, voltage range, layerheight, movement parameters, overhang controls, safety thresholds,leakage thresholds, short circuit determination threshold values, pixelmapping intervals and thresholds, debubble values, fusing, anodecleaning, islanding, distance to short, distance to short percentage,pixel limits, slow current control values, and maximum blob size. FIG. 1shows an illustrative layer description 111 for a first layer of anobject, which includes a target map 112 for the layer and processparameters 113 for the layer; subsequent layers have similar layerdescriptions with target maps and process parameters. The build planningstep or steps 102 may also generate overall process parameters 115 thatapply to all of the layers in the build, or that may be used as defaultvalues that apply unless a layer description overrides the defaults.

The build phase 120 of the process constructs an object from the buildplan 103, using for example equipment that performs electrochemicaldeposition. Illustrative equipment that may be used in one or moreembodiments of the invention is described below with respect to FIG. 2 .To initiate the build process, a surface of a cathode may be placed incontact with an electrolyte solution in step 121; the object may beconstructed by electrochemically depositing material onto the cathode bypassing current through an anode array that is also in contact with thesolution. Layers in build plan 103 may then be built successively ontothe base of the cathode or onto previously constructed layers,effectively enlarging the cathode for purposes of deposition. For eachlayer in the build plan, the layer description is retrieved or loaded instep 122. The layer description may for example be loaded into a memoryaccessible to a controller of the electrochemical deposition equipment;this controller may be any type or types of processors. For example, tostart object construction, the first layer description 111 may be loadedor retrieved. The controller may then perform step 123 to set or confirmthe relative position between the anode and the cathode. As layers aresuccessively built, the distance between the anode and the cathode mayneed to be modified so that the anode distance from the most recentlydeposited surfaces remains within a range that enables sufficientcontrol of the deposition process. For example, the electrochemicaldeposition equipment may include an actuator that can move either orboth of the cathode and the anode, as illustrated below with respect toFIG. 2 . For the first layer, step 123 may for example involve a“zeroing” procedure that sets the initial relative position between theanode and the cathode to a desired initial value. The specific methodsused for zeroing may vary depending on the deposition equipment. Forexample, in one or more embodiments the controller may move the cathodeor anode until one or more sensors indicate contact (or sufficientlyclose proximity) between the two, and it may then offset a desireddistance from this contacting position. In one or more embodiments theremay be sensors such as absolute or relative encoders on the positionactuator that assist in zeroing.

For layers after the first layer, step 123 may ensure that the relativeposition between the anode and cathode is correct to begin deposition ofmaterial for the new layer. In some cases this may require modificationsto the relative position, for example using an actuator that moves theanode or the cathode. For example, in some situations an object may beconstructed by successively depositing material for a layer, thenrepositioning the cathode relative to the anode to move the cathode awayfrom the anode to prepare for the next layer, and then depositingmaterial for the next layer. In other situations relative movementbetween the anode and cathode may be performed throughout constructionof a layer, sometimes referred to as “gliding,” so that no additionalrepositioning is required at step 123 when a new layer is loaded.

After a layer description is loaded in step 122, and the relativeposition of the cathode and anode is set or confirmed in step 123, thebuild process 120 enters an inner loop 140 of steps that may be executedto construct the loaded layer. As described above, this loop may be aclosed loop with feedback control, so that build steps and processparameters may be modified throughout the loop based on measuredfeedback signals. Step 125 may include various actions to depositmaterial via electrochemical reactions (for example, by passing currentthrough anodes) as well as actions that maintain or adjust the state orhealth of the anode array and the electrolyte. Illustrative maintenanceactions may include for example, without limitation, removal of bubblesfrom the electrolyte, agitation of the electrolyte to modify flow ratesor to modify distribution of ions in the electrolyte, and actions toremove films from anodes or to replenish anode surfaces. Any of thesemaintenance actions may be interleaved with deposition actions in anydesired manner.

At selected times or periodically during the construction of a layer,step 126 may be performed to obtain feedback signals that may forexample indicate how deposition is progressing. One or more embodimentsmay use any type or types of sensors to obtain feedback signals. Forexample, in one or more embodiments the current through each anode in ananode array may be measured (for example with a fixed voltage); a highercurrent may correspond to a lower impedance between the anode and thecathode, which may be correlated with the amount of material depositedon the cathode in the vicinity of each anode. In other embodiments, avariable voltage waveform may be used, and alternating current (AC)signals may be measured. One or more embodiments may use other feedbacksignals such as optical images of the cathode or distance measurementsto points on the cathode. In step 127 these feedback signals may beanalyzed to generate a deposition analysis 128, which may includeestimates of the amount of material deposited at locations within thelayer. Based on the deposition analysis 128, a determination 129 may bemade as to whether construction of the layer is complete. If the layeris complete, and if test 132 indicates that there are more layers to beconstructed, then a next layer is loaded in step 122 and the layerconstruction loop 140 is executed for that next layer; otherwiseconstruction of the object is finished. In some embodiments, thegeneration of deposition maps may be performed concurrently with thedeposition process. For example, additional sensing elements may beincorporated into the fabrication of the anode array to enablecontinuous characterization of the current flowing through eachdeposition anode, or the voltage at each deposition anode surface. Thiscould be performed, for instance, by an Analog to Digital converter(ADC) whose inputs are sequentially connected to successive rows ofdeposition anodes in a multiplexing method similar to that used in theaddressing of the anode array.

If test 129 indicates that deposition for a layer is not complete, thenin some situations the deposition analysis 128 or other data from thefeedback signals may be used to modify the parameters and controlsignals that are used to construct the layer. A test 130 may beperformed to determine whether any adjustments are required. If they arerequired, then one or more process parameters 131 may be modified, andthis may modify the control signals 124 that drive the deposition (andmaintenance) actions. As one example, if the deposition analysis 128indicates that enough material has been deposited in certain areas of alayer, then current may be turned off (or turned down) for anodescorresponding to those areas.

FIG. 2 shows an architectural diagram of illustrative equipment that maybe used to perform build steps of one or more embodiments of theinvention. The system has a printhead 200 that contains an array 201 ofdeposition anodes, and a corresponding array 202 of deposition controlcircuits for the deposition anodes. In one or more embodiments, thedeposition control circuits 202 may be organized in a matrixarrangement, thereby supporting high resolution anode arrays. Thedeposition anode array 201 may be organized in a two-dimensional grid;FIG. 2 shows a cross sectional view. A grid control circuit 203transmits control signals to the deposition control circuits 202 tocontrol the amount of current flowing through each deposition anode inanode array 201. Current flowing through the anodes is provided by apower distribution circuit 204 that routes power from one or more powersupplies 221 to the deposition control circuits and then to the anodes.Printhead 200 may also contain other elements such as insulation layers,for example to protect elements of the printhead from the electrolytesolution.

The deposition anode array 201 of printhead 200 may be placed in anelectrolyte solution 210. Electrochemical reactions may then causeplating of metal onto a manufactured part 230 that is coupled to cathode220. Intricate and detailed shapes may be built in part 230 by modifyingthe current flowing through each anode of deposition anode array 201.For example, in the snapshot shown in FIG. 2 , anode 211 is energized,so that metal is being deposited onto part 230 near this anode, butanode 212 is not energized so no metal is being deposited near thatanode.

In one or more embodiments, printhead 200 may be integrated with aprocessor 222. This processor may transmit signals to grid controlcircuit 203, which sends signals to the individual deposition controlcircuits 202 to turn anodes in deposition anode array 201 on or off (orto modify the intensity of current flow through each anode). Processor222 may be for example, without limitation, a microcontroller, amicroprocessor, a GPU, a FPGA, a SoC, a single-board computer, a laptop,a notebook, a desktop computer, a server, or a network or combination ofany of these devices. Processor 222 may be the same as or different froma processor or processors that analyze an object model to construct abuild plan. Processor 222 may communicate with one or more sensors 223that may generate the feedback signals that measure the progress ofmetal deposition on part 230. Sensors 223 may include for example,without limitation, current sensors, voltage sensors, timers, cameras,rangefinders, scales, force sensors, or pressure sensors. One or more ofthe sensors 223 may also be used to measure the distance between thecathode and the anode, for example for zeroing to begin manufacturing anobject, or to set or confirm the relative position between the anode andcathode at the beginning of each layer. The accurate positioning of thebuild plate relative to the electrode array at the initialization of thedeposition process may have a significant impact on the success andquality of the completed deposit. Embodiments may use various types ofsensors for this positioning, including for example, without limitation,mechanical, electrical, or optical sensors, or combinations thereof. Inone or more embodiments, mechanical sensors such as a pressure sensor,switch, or load cell may be employed, which detects when the build plateis moved and reaches the required location. In one or more embodiments,portions of the system may be energized, and the cathode may be moved toproximity to the energized component at a known location. When a voltageor current is detected on the cathode or build plate the build plate maybe known to be at a given location. One or more embodiments may useother types of sensors that detect for example capacitance, impedance,magnetic fields, or that utilize the Hall Effect to determine thelocation of the cathode/build plate relative to a known position. One ormore embodiments may use optical sensors such as laser rangefinders orsensors that detect interference with an optical path.

Either or both of cathode 220 and printhead 200 may be attached to oneor more position actuators 224, which may control the relative positionof the cathode and the deposition anode array. Position actuator 224 maycontrol vertical movement 225, so that the cathode may be raised (oralternatively the anode lowered) as the part 230 is built in successivelayers. In one or more embodiments position actuator 224 may also movethe cathode or deposition anode array horizontally relative to oneanother, for example so that large parts may be manufactured in tiles.The tiles may correspond to semiconductor dies. In some embodiments, anumber of tiles may correspond to the same semiconductor die patterns.In some embodiments, different interconnect structures may be built ontop of the same type of die, enabling customization of the resultingchips, even when the underlying dies are of the same pattern.

Printhead 200 may be connected to a power supply (or multiple powersupplies) 221, which supplies current 244 that flows through thedeposition anode array to drive metal deposition on part 230. Currentmay be distributed throughout the array of deposition control circuitsvia power distribution circuit 204, which may for example include one ormore power busses.

In one or more embodiments, the system may also include a fluid chamberto contain the electrolyte solution (not shown in FIG. 2 ), and a fluidhandling system (also not shown). The fluid system may include forexample a tank, a particulate filter, chemically resistant tubing and apump. Analytical equipment may enable continuous characterization ofbath pH, temperature, and ion concentration using methods such asconductivity, High Performance Liquid Chromatography, mass spectrometry,Cyclic Voltammetry Stripping, spectrophotometer measurements, or thelike. Bath conditions may be maintained with a chiller, heater and/or anautomated replenishment system to replace solution lost to evaporationand/or ions of deposited material.

Although the system shown in FIG. 2 has a single array of depositionanodes, one or more embodiments may incorporate multiple depositionanode arrays. These multiple anode arrays may for example operatesimultaneously in different chambers filled with electrolyte solution,or they may be tiled in a manner where the anode arrays work together todeposit material on a shared cathode or series of cathodes.

FIG. 3 shows illustrative elements of a build plan for an object with anobject model 101 a. The object model 101 a may be for example a 3D CADmodel, or any description of the geometric or material properties of anobject. The build planning process may slice this model into layers, andmay develop a layer description for each layer. FIG. 3 shows fourillustrative layers, each of which corresponds to a horizontal slicethrough model 101 a. Build plans may have any number of layers andslices may be of any desired thickness, shape, and orientation.Associated with each layer is a layer description that includes a targetmap, and one or more process parameters. The four layers shown in FIG. 3have target maps 112 a through 112 d, and process parameters 113 athrough 113 d, respectively. The target map may for example be atwo-dimensional image that shows where material is to be deposited inthe layer. In FIG. 3 the target maps are shown with black pixelsindicating that material is to be deposited at the corresponding layerposition, and white pixels indicating that no material is to bedeposited. In one or more embodiments the target map may have non-binaryvalues at positions; for example, target maps may be described asgrayscale images. In one or more embodiments, target maps may haveadditional information such as the type of material or materials to bedeposited at each location.

FIG. 3 shows three illustrative process parameters 301 through 303 foreach layer. One or more embodiments may associate any number of processparameters with layer descriptions. A process parameter may describe anyfactor that affects the manufacturing of a layer or that affects anymaintenance activities to be performed. Illustrative parameter 301defines the current density that may be set to construct the layer,which is specified for example as a percentage of the maximum currentdensity supported by the manufacturing equipment. Illustrative parameter302 indicates whether a layer may require lateral deposition ofmaterial. This parameter may be based on whether the build planningsystem detects overhangs, as described below with respect to FIG. 6 .For layers that do not require lateral deposition, in one or moreembodiments the manufacturing system may reposition the cathodevertically relative to the anode throughout the manufacturing of thelayer, so that deposited material remains at a relatively fixed distancefrom the anode as it accumulates on the layer; this “gliding” movementmay for example reduce the chance of short-circuits developing betweenthe anode and the cathode. Illustrative parameter 303 is the targetheight of the layer. In some situations the layer height may be higheron initial layers (such as layer 112 d) to allow for easier bubbleclearing. Layers with overhangs (such as layer 112 b) may have lowerheights to allow them to build with more dimensional stability, forexample.

Process parameters for a layer may also include the target output fromeach anode in the anode array when constructing the layer. In simplesituations this output may match the target map for the layer: anodesmay be turned on if they are in the position where material is to bedeposited, and turned off otherwise. In other situations therelationship between anode output and the target map may be morecomplex, as illustrated for example below with respect to FIGS. 11A,11B, 11C, and 12 .

FIG. 4 illustrates density manipulation on the base layer 112 d ofobject 101 a. This layer is added first to the cathode, and other layersare then constructed on top of the base layer. For a base layer (or aset of base layers) in particular, it may be beneficial to reduce thelayer density to make the layer porous. The porosity of the layer maymake it easier to remove the object from the cathode after manufacturingis complete. Density may be reduced by manipulating the target map toreduce the number of pixels where material is to be deposited. Forexample, deposition may be turned off at random positions with aprobability equal to 100% less the target density. In FIG. 4 , thedensity 401 parameter is applied to the original target map 112 d togenerate a modified target map 402, where 70% of the pixels of theoriginal target map have been turned off (“off” pixels are shown aswhite in the image). This modified target map 402 results in base layer403 deposited onto cathode 220 (shown as a vertical cross section inFIG. 4 ). Additional layers 404 are constructed on top of the base layerto form the complete part. Removal 405 of the part from the cathode 220may be facilitated by the porosity of the base layer 403.

FIGS. 5 and 6 show illustrative build planning and manufacturing for alayer that has significant overhang. Overhangs are features that extendhorizontally without material to support them in the layer below. Intraditional 3D printing with plastics, supports must often be addedexplicitly to support these overhangs, and then removed in apost-production step. For electrochemical additive manufacturing, manyoverhangs can be constructed directly, without supports, since metalions can accumulate laterally and fuse to the overhang structure withsufficient strength that underlying supports may be unnecessary. FIG. 5illustrates how overhangs may be identified in one or more embodiments.The target map 112 b of a layer may be compared to the target map 112 cof the layer underneath (or to several such layers), for example with adifferencing operation 501. This comparison yields a delta map 502,which shows areas 503 where material is being added without materialbelow. If the size of these areas within 503 are sufficiently large, thebuild planning system may make a determination 504 that the overhangsrequire special processing such as lateral construction, as illustratedin FIG. 6 . FIG. 6 shows illustrative steps to manufacture a smallportion 601 b of the overhang of layer 112 b above area 601 c in thelayer 112 c below. This portion 601 b is effectively a “bridge” thatrests on two supporting columns below. The columns 610 have beenconstructed in previous layers, with the top of these columnscorresponding to region 601 c of target map 112 c. Construction of thebridge proceeds in three illustrative sub-steps within layer 112 b.First, material 611 is added on top of columns 610; this sub-stepcorresponds to a subset 621 of the target map 112 b. Second, material612 is added laterally out from the columns, corresponding to a subset622 of the target map 112 b. Third, material 613 is added laterally inthe middle, corresponding to a subset 623 of the target map 112 b,resulting in final structure 614. The number of lateral build stepsrequired may vary based for example on the size of the overhang and onthe binding strength of the material.

In one or more embodiments, overhang processing may also includereducing the height of layers in the regions of overhangs in order toachieve the deposit required. This may be done for example by changingthe layer height to make the overhang distance match some ratio of thepixel pitch. For example, with a 45 degree overhang and a pixel pitch of50 um, the layer height may be set to 50 um, which will cause theoverhang distance to be 50 um (1 pixel width). On a 60 degree overhang,the layer height would be ˜29 um in order to have an overhang distanceof 50 um. These two examples show a 1:1 ratio, where the overhangdistance is increased by 1 pixel per layer. For a 2:1 ratio, the layerheights would be doubled, resulting in an overhang distance of 100 um or2 pixels for each layer. This may be done because it results in a morestable and consistent build of the overhang regardless of overhangangle.

FIGS. 7 through 10 show illustrative feedback signals and analysis ofthese feedback signals to determine whether a layer is complete or tomodify process parameters for layer manufacturing. FIG. 7 shows anillustrative method of feedback based on current sensors 223 a that mayfor example be connected to the anodes of the deposition anode array201. Current sensors may be used to estimate the extent of depositionproximal to each anode in the anode array, since the impedance betweenan anode and the cathode may vary based on the proximity of the anode tothe deposited conductive material on the cathode. For example, anodesmay be set to a known voltage, and the current flowing from each anodemay then be inversely proportional to this impedance. FIG. 7 showsillustrative anodes 701 through 706, and an illustrative part 230 a thathas been partially constructed. Current sensors 223 a measure currents710 through each anode. For anode 703, the anode has formed ashort-circuit with the deposited material; thus the measured current 713is very high. For anode 704, the anode is very close to the depositedmaterial, but is not quite short-circuited, so the measured current 714is below the level 713 of the short-circuited anode 703. Anode 701 isfar from the deposited material, so the measured current 711 is verysmall.

In one or more embodiments, the feedback signals such as current sensordata 710 may be processed further to generate an analysis of the extentof deposition at locations within the part. This processing may forexample be based on known or estimated relationships between the extentof deposition and the feedback signals. FIG. 8 shows an illustrativeanalysis of a two-dimensional map 801 of current measured by currentsensors 223 a. In this map 801, brighter pixels correspond to highermeasured current. Analysis 127 of the current map 801 may for exampleapply a thresholding operation 802 to select pixels that exceed aspecified current level, resulting in preliminary deposition analysis128. This illustrative deposition analysis 128 is a binary image, withwhite pixels showing regions of high deposition and black pixels showingregions of lower deposition. Thresholding operation 802 is illustrative;one or more embodiments may analyze feedback signals 801 in any desiredmanner to generate a deposition analysis. The deposition analysis 128may then be used to make determination 129 of whether deposition of alayer is complete, and determination 130 of whether modifications to anyprocess parameters are needed for continued construction of a layer.FIGS. 9A and 9B show an illustrative analysis 129 to determine layercompleteness, and FIG. 10 shows an illustrative analysis 130 of how tomodify process parameters.

FIG. 9A shows an illustrative process to compare deposition analysis 128to a layer target map 900 to determine whether manufacturing of thelayer is complete. The target map 900 indicates where material should bedeposited in the layer, with black pixels corresponding to material andwhite pixels corresponding to no material. The deposition analysis 128shows areas of high current, which may for example indicate areas ofshort circuits where the anode and deposited material are in contact orare very close. In one or more embodiments, the deposition analysis 128may be further processed to form an estimate of where material has beendeposited in the layer. For example, image 128 may be modified using anytransformations including for example, without limitation, morphologicalfilters, linear or nonlinear filters, or Boolean operations.Illustrative operation 901 shown in FIG. 9A is a dilation operation(which is a morphological filter); this operation expands regions ofwhite pixels by adding pixels out from the region boundaries. Theresulting modified map 911 may provide an improved indicator of wheredeposition has occurred, since for example locations close toshort-circuited anodes may also have high levels of deposition. Thismodified map 911 may then be compared to the target map to determine theextent to which the estimated deposition matches the desired depositionfor the layer. First the target map 900 may be inverted in operation902, so that in both the resulting inverted target map 912 and themodified deposition analysis 911 the white pixels correspond todeposition locations. A count 913 of the white (“on”) pixels in invertedtarget map 912 indicates how many positions in the layer should receivedeposited material. The modified deposition map 911 and the invertedtarget map 912 may then be ANDed in operation 920; the resulting map 921shows the pixels that correspond to positions that should have depositedmaterial (according to the target map) and that do have depositedmaterial (according to the deposition analysis). The count 922 of white(“on”) pixels in 921 may then be compared to the count 913 of desired“on” pixels; the ratio of these values 923 is a percentage of completionmeasure for the layer. In one or more embodiments, this completionpercentage ratio may be compared to a threshold, and the layer may beconsidered complete when the threshold percentage is reached orexceeded. The operations 901, 902, and 920 shown in FIG. 9A areillustrative; one or more embodiments may apply any transformations oroperations to the deposition analysis 128 or the target map 900 todetermine whether a layer is complete, including but not limited tomorphological operations such as 901 or Boolean operations such as 902and 920.

One potential limitation of the method illustrated in FIG. 9A is that itis possible for the overall completion percentage for a layer to behigh, while completion may be low for specific subregions of the layer.In some situations it may be important that subregions of the layer allbe completed to a high percentage. FIG. 9B shows an illustrativeextension of the method of 9A that applies a completion threshold tosubregions. In one or more embodiments, subregions may be defined in anydesired manner. For example, a layer may be divided into a regular gridof tiles of any resolution, and completion criteria may be applied toeach tile. FIG. 9B illustrates an approach that divides the target mapinto “islands” of connected components, and that applies completioncriteria separately to each island. Target map 912 (inverted as in FIG.9A so that white pixels correspond to desired deposition) has fourislands 912 a through 912 d; each island is a connected component anddifferent islands are not connected. The modified deposition analysismap 911 is partitioned into these island regions, resulting in fourdeposition analyses 921 a through 921 d, corresponding to the islands912 a through 912 d. Within each of these island deposition analyses,the percentage of white (“on”) pixels indicates the level of completionof deposition within the associated island. These individual islandcompletion percentages 923 a through 923 d may then be analyzed todetermine whether the layer is complete. For example, a threshold may beapplied to each of the island completion percentages, and the layer maybe complete only when all of the islands meet or exceed this threshold.In one or more embodiments, different completion criteria may be appliedto different islands, and the overall layer may be complete only wheneach island meets its respective completion criterion.

In one or more embodiments, completion criteria for a layer or forindividual islands may be based on other factors instead of or inaddition to a percentage of completion of desired deposited pixels. Forexample, a layer or an island may be considered complete if all or acertain number or fraction of pixels within the layer or island wheredeposition is desired are within a specified threshold distance of oneor more deposited pixels. The set of pixels where deposition is desired,and the set of pixels where deposition has occurred (to a desired levelof completion) may be determined as described above. In someembodiments, elapsed time of deposition, charge used for deposition,overall current, and/or impedance between the electrodes may be used aspart of the determination whether a layer is done.

FIG. 10 shows an illustrative example of how the deposition analysis 128may be used to adjust process parameters during the construction of theassociated layer until the layer is determined to be complete. As forcompletion analysis, the deposition analysis 128 may first betransformed using any type of filters or operations. FIG. 10 shows anerosion operation 1001 applied to the deposition analysis 128 togenerate a modified deposition analysis 1002. This erosion operation1001, which is an example of a morphological filter, shrinks regions ofwhite pixels by removing pixels from region boundaries. The resultingmap 1002 therefore may represent a more conservative estimate of wheredeposition has occurred. The erosion operation 1001 is illustrative; oneor more embodiments may apply any type of transformation to depositionanalysis 128, including for example, without limitation, morphologicalfilters, linear or nonlinear filters, or Boolean operations. Modifiedmap 1002 may then be inverted in operation 1003 to yield map 1004, wherethe black pixels correspond to the eroded regions of deposition, and thewhite pixels correspond to locations with potential lack of sufficientdeposition. This map 1004 may then be ANDed with the inverted target map912, yielding a map 1006 that may be used to modify the processparameters for further construction of the layer. In this map 1006,white (“on”) pixels correspond to locations where deposition is desiredbut may not yet be sufficiently complete. This map may therefore be usedto set the outputs 1007 of the anodes in the anode array, so thatdeposition continues for anodes that correspond to the “on” pixels ofmap 1006. Anode outputs may be set for example by setting anode currents1011, by setting anode voltages 1012, or by setting anode duty cycles1013, or by using a combination of these methods.

FIG. 10 illustrates feedback control that generates essentially binarycontrol signals for anodes, such as map 1006. Anodes may then be turnedon or off based on these control signals. In one or more embodiments,anode control (or control of any other process parameters) may usenon-binary control signals; for example, anode currents may be variedcontinuously from zero to a maximum value based on analysis of thefeedback signals.

Although use of high resolution anode arrays may provide fine control ofdeposited material, in some situations the pattern of deposition ofmaterial onto the cathode may not correspond precisely to the pattern ofanode outputs. One or more embodiments may therefore adjust the anodeoutputs by pre-processing the target map to account for these effects.FIGS. 11A, 11B, 11C, and 12A illustrate this process using aone-dimensional model of anode arrays for ease of presentation. Similarconcepts may be applied in one or more embodiments to two-dimensionalanode arrays; an example in two dimensions is shown in FIG. 12B.

FIG. 11A shows illustrative deposition 1111 onto cathode 220 when only asingle anode 1101 of anode array 201 is energized. In some environments,material may be deposited onto the cathode at positions that are notdirectly across from the energized anode. For example, deposition 1111may occur in an approximately Gaussian pattern that is centered acrossfrom an energized anode, and that spreads out laterally from thiscenter. FIG. 11B shows an illustrative deposition pattern 1112 whenmultiple anodes 1101, 1102, and 1103 are energized. In this scenario,the deposition pattern may be approximately the sum of the depositionpatterns from each of the individual anodes 1101, 1102, and 1103. Inparticular, FIG. 11B illustrates that deposition may be higher at thecenter (across from anode 1101) than at the edges, due to the additiveeffects from all three of the anodes.

If deposition patterns from individual anodes combine additively, thegeneral effect of the phenomena shown in FIGS. 11A and 11B may be tomodify the pattern of anode outputs via a convolution 1141 with a pointspread function 1140 that describes the spread of deposition from asingle anode point source. FIG. 11C shows an illustrative pattern 1130of anode current that is constant within a range from 1121 to 1122, andzero outside this range. Because of convolution 1141, the actualdeposition thickness will not match the input shape 1130, but insteadwill have shape 1150 with higher accumulation in the center, and withsome deposition extending beyond the bounds 1121 and 1122. Effectivelythe sharp corners of the anode current pattern 1130 are smoothed by theeffects shown in FIGS. 11A and 11B. One or more embodiments maytherefore modify the anode currents to account for this convolution 1141or for other effects that distort the deposition pattern. FIG. 12A showsan illustrative approach that may be used in one or more embodiments.Based on a target map 1201 that describes the target thickness of alayer as a function of position, the build planning process may performa deconvolution 1210 or other transformation to reverse the effects ofthe distortion illustrated in FIGS. 11A through 11C. For example, targetmap 1201 with a constant thickness between bounds 1121 and 1122 may bedeconvolved to an anode current pattern 1211. To compensate for thedispersive effects of the deposition point spread function, theillustrative anode current has a higher value 1212 at the edges, andsome anodes such as 1214 within the central region of the rectangularpattern may be turned off entirely. In addition, some anodes such asanode 1213 may have nonzero currents even if they are outside the bounds1121 and 1122. These effects are illustrative; one or more embodimentsmay generate any desired anode current pattern 1211 to achieve thedesired layer thickness pattern 1201. Transformations 1210 may includeany deconvolution methods or any other function transformation or imageprocessing methods. These transformations may be based on anymeasurements or models of the deposition process, including for examplea point spread function 1140 that describes how anode currents aremapped to deposition patterns.

FIG. 12B shows a two-dimensional example of transformation of a targetmap into a desired anode current pattern. Target map 1220 shows areas ofdesired deposition (in black) for a particular layer of a part build. Asdescribed above, transformations 1210, which may for example includedeconvolution or any other type of image processing, may be applied tothis target map 1220 to generate a pattern 1230 that indicates the anodecurrent pattern that may be generated to achieve the desired deposition.In this example, anodes are turned on for the anodes that correspond toanodes with desired deposition, and additional anodes (shown ascross-hatched regions) are turned on around the edges and the corners ofthe deposition area. For example, edge anodes are turned on around eachouter edge, such as anodes 1231 along the top edge, and additionalanodes are turned on around the corners, such as anodes 1232 around thetop right corner. Turning on these additional edge and corner anodeshelps to shape the field of current to drive deposition of material moreevenly at the corresponding edges and corners of target map 1220.

One or more embodiments may also modify anode currents over time in apreprogrammed or adaptive pattern, as illustrated in FIG. 13 . Forexample, in one or more embodiments, subsets of anodes may besuccessively switched on and off during the manufacturing of a layer.This alternation may for example compensate for potential depletion ofmetal ions in the electrolyte that might occur if anodes output aconstant current throughout the construction of a layer. It may alsoprevent formation of bubbles in the electrolyte. In the example shown inFIG. 13 , target map 112 e has a square central area 1301 where materialis to be deposited. Instead of constantly emitting current from all ofthe anodes that correspond to this region 1301, one or more embodimentsmay alternate current from two subregions 1311 and 1312, which partitionthe region 1301 into a checkerboard pattern. During phase 1321, anodesin region 1311 emit current 1331, and anodes in region 1312 are switchedoff; during phase 1322, anodes in region 1311 are switched off, andanodes in region 1312 emit current 1332. This alternation may forexample allow ions 1310 in the electrolyte to diffuse into the regionsadjacent to the switched-off anodes so that these regions are notdepleted. The checkerboard pattern of regions 1311 and 1312 isillustrative; one or more embodiments may divide anodes into any numberof regions of any shape and size, and may switch anodes of these regionson and off in any desired pattern with any desired duty cycles.

FIG. 14 shows illustrative maintenance actions that may be performedduring the manufacturing process in one or more embodiments. Theseactions may for example be interleaved with deposition, or they may beperformed between manufacturing of layers. The actions shown areillustrative; one or more embodiments may perform any desiredmaintenance activities at any point in the manufacturing process. FIG.14 shows three illustrative issues that may arise during manufacturingthat may require maintenance activities. First, anodes in the anodearray 201 may erode, such as anode 1401, and may need to be replenishedor resurfaced. Second, films such as film 1402 may form over anodes andprevent them from effectively driving deposition onto the cathode.Third, bubbles such as 1403 may form in the electrolyte between theanode array and the deposited material 230.

Over time, anodes such as anode 1401 may erode, even if anodes areconstructed of a largely insoluble material. One or more embodiments mayperiodically or as-needed reverse this erosion using a secondary anode1410. The deposition process may for example be paused and the powersupply 221 may be reversed using switches 1411 and 1412, so that theanode array temporarily acts as a cathode, and the secondary anode 1410acts as the anode. Current flowing from the secondary anode 1410 maythen cause material 1413 to flow from the secondary anode to the erodedanodes in array 201. The secondary anode 1410 may for example be a largebulk anode that is composed of an inert material like platinum. Thesecondary anode may be composed of the metal that is used forelectrodeposition, such as copper for example; this metal will dissolveand plate onto the anodes of anode array 201 without depleting the metalin the electrolyte solution. When the switches 1411 and 1412 arereversed again, the metal plated onto the anode array then plates ontothe cathode.

In some cases, target deposition material (such as copper from a copperelectrolyte bath) may end up plated onto a surface of the electrodearray as a film 1402. This film of target material may bridge betweenmultiple deposition electrodes and may impact their ability to beindividually addressed. A film may be detected from the feedbacksignals, for example when a group of adjacent anodes shows an abnormallyhigh current. A film may be removed for example by moving cathode 220far away from the anode array and activating the anodes covered by thefilm. This action dissolves the film while not causing an unintendeddeposit on the cathode.

During electrolysis, bubbles 1403 may form in the space between theanode array 201 and the part 230. Bubbles may be removed for example bymanipulating or modifying the flow 1420 of electrolyte, for example withpumps or agitators, or by inducing vibrations 1421 in the electrolyte todissipate the bubbles. Vibrations may be introduced into the electrolyteusing a vibration oscillator in contact with the electrolyte, or byvibrating the cathode, anode array, or reaction chamber. Flowmanipulation may also include purposefully increasing the distancebetween the build and the anode array to allow for greater fluid flowand/or bubble removal, while either keeping the anodes energized orde-energized until the flow manipulation is complete.

In one or more embodiments, all or portions of the feedback signals,control parameters, and deposition analyses measured or generatedthroughout a build of a part may be maintained as quality controlrecords. This data may be used for any or all of several purposes,including for example facilitating or eliminating part inspections,supporting certification of parts or manufacturing processes, andpost-mortem analysis of part failures or part performance issues. Inaddition to providing detailed tracing for the specific manufacturingsteps and parameters used for each part, this quality control data maybe aggregated across parts, lots, or facilities and used for statisticalprocess control and for continuous process improvement. For example,data on part performance in the field (such as failure rates or partlifetimes) may be correlated with the part quality control data todiscover correlations between process parameters and part performance;these correlations may then be used to improve future part buildprocesses. In one or more embodiments, machine learning techniques orother artificial intelligence techniques may be used to automaticallydiscover relationships between build record information and partperformance. For example, analysis of large numbers of parts and theirassociated quality control records may show that a lower current densityfor particular types of layers results in higher part failures; amanufacturer may use this type of information to modify build processesto reduce future failure rates. When relationships between buildparameters and part performance are discovered, the database of buildquality information for parts may be used to predict failures forpreviously built parts, allowing them to be potentially recalled orreplaced prior to failure.

FIG. 15 shows an illustrative part 1501 that was manufactured using anembodiment of the invention. Feedback control of the manufacturingprocess using techniques described above enables the extremely fineresolution and high quality of this completed part.

In one or more embodiments, a manufacturing process such as theprocesses described above may enable addition of interconnectionfeatures, heatsinks, or similar structures to a plate, such as a siliconwafer, for example. Interconnection structures may be referred to forexample as “wafer bumps”, or “pillars.” Precisely formed, electricallyconductive interconnection structures are a critical component insemiconductor and electronics packaging. Increased technological demandsare driving an increase in interconnect density per area, or packing ina greater number of thinner, taller features with smaller distancebetween them. Electrochemical additive manufacturing offers thepotential of constructing more effective interconnection structurescompared to processes currently known in the art.

A typical wafer bumping fabrication process is relatively complex andinvolves multiple steps—first is the deposition of a conductive, oftenmetallic film, as a “seed” layer, second is the application, exposureand development of a photoresist to define the locations in which bumpsare desired, then an electrodeposition step to deposit the material intothe openings defined by the photoresist. Finally, the photoresist andseed layers are removed leaving independent electrically isolatedstructures on the substrate.

Further, since the photoresist defines the regions and sidewalls of thedeposited bump material, the primary limitation in bump geometry andspacing is driven by the capabilities of the photoresist, includingaspect ratio (vertical feature dimension vs. horizontal featuredimension) that the photoresist is capable of resolving, minimumdiameter, maximum overall height, and spacing between adjacent bumps.Another issue with photoresist based processing is the requirement tocreate a new mask whenever a new connection pattern is desired. Thus, awafer bumping process that reduces or eliminates the reliance onphotoresist sub-processes is desired not only from a manufacturing costand time efficiency perspective, but also to enable higher performanceinterconnect structures.

FIG. 16 illustrates addition of wafer bumps using electrochemicaladditive manufacturing, which may provide benefits such as thosedescribed above. An objective is to add wafer bumps or similarstructures to a plate 1601, which may be for example a silicon wafer orany type of substrate onto which circuits or components are placed.Plate 1601 may be of any size or shape, and it may be made of anymaterials. It may contain one or more tiles such as illustrative tile1602; each tile may for example contain a circuit or circuits, orisolated electronic or electrical components. Typically it is desired toadd conductive structures to one or more surfaces of the plate. Thesestructures may be for example electrically conductive, thermallyconductive, or both. They may serve, for example, as interconnections toother circuits or devices, they may serve as heat sinks to remove heatfrom circuits on plate 1601, or they may perform mechanical functionssuch as alignment or attachment. To construct these structures, plate1601 may be connected to cathode 220 in an apparatus similar to theapparatus described with respect to FIG. 2 . Current flows from anodesin deposition anode array 201 through electrolyte solution 210 that isin contact with the surface of the plate, resulting in deposition ofinterconnect structures such as bump 1603. The amount of current flowingfrom each anode is controlled in order to deposit material for theconnection structures in a precise pattern. The completed plate 1611 mayhave multiple interconnect structures throughout the plate. Illustrativecompleted tile 1612 within plate 1611 has five wafer bumps, eachconnected to a corresponding connection point in a circuit 1613 that iswithin or proximal to the tile; for example, bump 1603 is connected toconnection point 1614 of circuit 1613.

FIG. 17 shows a flowchart of illustrative steps that may be used in oneor more embodiments to fabricate interconnection structures or similarfeatures on a plate. In step 1701, a plate is obtained; the plate maycontain one or more tiles, each of which may contain one or moreconnection points. The plate may have a conductive seed layer, which mayfor example be deposited onto a surface of the plate. In step 1702, theplate is coupled to a power supply (for example via attachment to acathode as in FIG. 16 ); for example, this attachment may create anelectrical connection to the conductive seed layer of the plate. In step1703 a surface of the plate, such as a surface of the seed layer, isplaced into contact with an electrolyte solution. In step 1704, theplate is aligned precisely with the anode array; this alignment may setthe relative position and orientation of the plate and anode array byrepositioning one or both of them. In step 1705, current is passed fromanodes in the anode array through the electrolyte to construct theinterconnection features.

Step 1705 may construct the features layer by layer, as described above.Layers may be of any height. The inventors have discovered that shorterlayer heights may lead to better deposit quality, and may require lowerplating voltages and current densities. Illustrative layer heights usedin one or more embodiments of the invention are 5 microns or below; oneor more embodiments may use layer heights of below 1 micron for improvedcontrol and deposit quality. In some situations it may be advantageousto have a higher than normal current density or anode voltage, and/or ashorter than normal layer height on the initial layers to assist withforming the initial deposit localization. In some cases it may beadvantageous for the final (top) layers of a deposit to have differentparameters from the rest of the print for the purposes of guaranteeing ahigher quality surface finish for the sides and top of the deposit. Thiscan be achieved for example by increasing the working distance to agreater distance than used in the rest of the build and reducing thecurrent. For instance, if a working distance of 10 microns per layer isused for the majority of a build, an increase to 25 microns or morecould be used. This blankets the deposit in a less localized, highquality layer of material.

During step 1705, feedback control techniques including those describedabove may be used to control the manufacturing process. Illustrativefeedback control methods may include for example measuring the currentthrough each anode. Current may be measured by turning on one anode at atime and measuring the current through the entire anode array.Alternatively in one or more embodiments a voltage sensing analog todigital converter may be connected to each anode's surface. When thisvoltage drops, it indicates that the deposit has gotten close to ortouches the anode and the anode is now grounded. By knowing theresistance of the pixel, the voltage drop at the anode (surface voltageless supply voltage) can be divided by the anode's resistance tocalculate an anode current. This technique has the benefit of providingcurrent mapping data without stopping the deposition process, as well asproviding the actual anode currents during deposition—thus revealing forexample a solution depletion effect that would not be visible if onlysensing one anode at a time.

Based on the feedback signals (such as current or voltage measurements),the system may modify the flow of current through individual anodes.Anodes may be turned on or off (binary control), or the amount ofcurrent through anodes may be varied (continuous control). To turn ananode off, it may switched to a high-impedance mode (not ground) to stopthe flow of current through the electrode. Alternatively, in one or moreembodiments, anodes may be turned off by setting the anode to aprescribed voltage rather than a high impedance state. This voltage maybe selected specifically to be greater than 0V or ground potential, butlower than the voltage at which current flows through the anode.Generally an electrochemical system is defined by the combination ofanode material, bath makeup and electrode geometry (size/spacing) andresults in a nonlinear relationship between anode voltage and systemcurrent. For each electrode and bath combination this relationship canbe characterized to understand the voltage at which an electrodepotential can be maintained without appreciable current being passed ormaterial being deposited. More specifically, this voltage may be higherfor Platinum than for Copper when used as an anode. When a platinumelectrode is found to have a copper film the electrode can be set to thecopper threshold voltage; the copper will pass current and dissolve intosolution but once all the copper is removed the potential will not be ata high enough potential to pass significant current through the system.Anode or system current can be measured to characterize when Cu filmremoval is complete. In some cases, it might be desired to leave ananode energized for a period of time even after a short has beendetected on that anode. This method may impact the condition of the topsurface of the deposit and the diameter of the feature as it grows.

Continuous variation in anode current may be useful because differentlocations in the deposit may require lower or higher current densities.For instance, in an array of bumps with all anodes addressed to an equalcurrent density, those on the interior of the array build faster andthicker, with those on the edges resulting in less material and in thecorners even less. This difference can be characterized and compensatedfor by addressing different voltages/current densities to anodes basedon their position, size, or other measurements (even real time currentmeasurements, for instance if ions are depleted at one location). Insome embodiments, however, the anodes in the anode array may becontrolled in groups or as one group. In these types of embodiments,each interconnection column may correspond to an anode of the anodearray. In some embodiments, for a device that requires thousands offeatures to be deposited, the corresponding anode array may befabricated with thousands of individually controlled anodes. This isdistinguished from an application with multiple anodes when the numberof anodes is much smaller than the number of features, such as thosethat may be used in some mask based systems.

In some embodiments, several anodes in the array may be energized toform a contiguous deposit, for instance a single square deposit ofdimension 45 micron×45 micron could be equally achieved by activating a3×3 grid of anodes on a uniform grid of 15 micron spacing.Alternatively, various sub-pixel geometries can be employed to helpmodulate the electric field and provide greater control over the growthof the deposit. For instance, central anode elements and external anodeelements to compensate for variations in deposition uniformity of adeposit from the center to the external diameter.

FIGS. 22A, 22B, and 22C illustrate three example types of electrodeconfigurations: FIG. 22A illustrates non-independent electrodes,non-independently controlled; FIG. 22B illustrates independentelectrodes, non-independently controlled; and FIG. 22C illustratesindependent electrodes, independently controlled, which may beimplemented using an anode array, for example.

FIG. 22A illustrates an embodiment in which the anodes arenon-electrically independent and are also non-independently controlled.Three illustrative anodes, 2201, 2202, and 2203, may for example befabricated by taking a conductor 2204 and simply masking openings 2205and 2206 on its surface. When placed in proximity to the substrate,independent deposits will begin to form but since the electrodes are notelectrically isolated, when the deposit grows enough to create a shortcontact between the anode and cathode, current preferentially flowsthrough that deposit rather than through the solution to form theremaining deposits. This shorting effect may be mitigated by carefulattention to the deposition current to detect impending contact followedby adjustment of the anode/cathode gap.

In the embodiment illustrated in FIG. 22B, illustrative anodes 2211,2212, and 2213 are electrically independent, but not independentlycontrolled. The electrodes may be electrically independent in that eachis isolated from the other anodes with, for instance, a resistor. Forexample, anodes 2211, 2212, and 2213 are isolated via resistors 2214,2215, and 2216, respectively. When a group of anodes is activated, theirdeposits will grow, and when one deposit grows to touch its respectiveanode, the isolating resistors serve to limit the short circuit currentflowing through that anode, enabling current to flow through theremaining anodes and continue growing their respective deposits.

In the embodiment illustrated in FIG. 22C, each of the illustrativeanodes 2221, 2222, and 2223 are individually and independentlycontrolled, via corresponding switches 2224, 2225, and 2226,respectively. Note that while the switches are illustrated using knifeblade symbols, the switches may be of multiple types and may provideindependently controlled non-binary (analog) control signals to theanodes.

FIG. 18 shows a variation on the apparatus illustrated in FIG. 16 ,which may be used in one or more embodiments to constructinterconnection features or other structures. In this illustrativeapparatus, the anode array 201 is vertically above the plate 1601 andthe cathode. The plate 1601 may be held in position using methods knownto the art of semiconductor manufacturing. These may include mechanicalclamping, vacuum chucks, and the like. In some cases, an electricalconnection is made to the surface of the substrate. This electricalconnection can be through the clamping assembly, or as a separate clip.The plate may have been previously coated with a conductive “seed” layer1601 a to which the electrical connection is made. In the example shownin FIG. 18 , plate 1601 is held in position via clamps or chucks 1801 aand 1802 a, and 1801 b and 1802 b. Any number of clamping points may beused in one or more embodiments. Connectors 1801 a and 1801 b makeelectrical contact with conductive seed layer 1601 a of plate 1601,coupling the seed layer to the ground of the power supply circuit sothat it acts as the cathode for electrodeposition.

A mechanical positioning system may be used to set, modify, and maintainthe relative position and orientation between the anode array 201 andthe plate 1601. In some embodiments, it may be used to maintain aconsistent gap between the deposited material's surface and the anodearray as the deposit forms. It may also align the anode array relativeto the plate to ensure that deposition of structures happens in thedesired locations. The orientation of the anode array relative to theplate may be controlled to ensure that the anode array is substantiallycoplanar to the plate. The mechanical positioning system may alsoinclude sensors to determine the relative location between the anodearray and the plate, including for example, without limitation linearpotentiometers, Linear Variable Differential Transformers (LVDT), Halleffect, capacitive, Laser rangefinder, laser and other similar linearencoder types. Sensors may for example use optical or electrical methodsof inspecting the plate position or orientation relative to the anodearray. For example, in some embodiments a high magnification opticalsystem may view the positions of alignment marks on both the anode arrayand the plate and determine their relative offset. In one or moreembodiments a notch or flat section of the plate may be used to alignthe apparatus to the plate and to approximately locate the features onthe plate. It is possible that in some embodiments that measurements maybe taken using the anode array itself to determine the coplanarity ofthe anode and substrate. These measurements could include for example, acapacitance reading using the seed layer of the substrate, or voltage orcurrent, or A/C impedance measurements between the anode and substrateeither in air or the plating bath to determine the distance between thesurfaces at various locations in the build volume. The coplanarityalignment of the anode array relative to the substrate is alsoimportant. This, for instance, can be done by incorporating multiplesensors to characterize the gap between the anode and cathode at variouslocations, for instance using a capacitive or laser sensor. Using thedifferences in these gap measurements the anode array or substrate (orboth) can then be moved to bring the planes of each into alignment.Knowing that a typical substrate size could be a 300 mm wafer, and thatthe feature targeted to be manufactured is a pillar 30 microns indiameter and less than 100 microns tall, gap measurement and alignmentaccuracy of approximately one micron or less may be required forsuccessful pre-deposition alignment.

To begin deposition of material onto the plate, one or more embodimentsmay use an initial zeroing process to place the anode array and theplate into the appropriate starting positions. For example, zeroing maybe performed in one or more embodiments with a position sensor whichsenses the gap between the anode and cathode. The mechanical positioningsystem may be activated to move the anode array closer to the cathode;once the position sensor starts sensing less displacement than thecommanded distance, the system determines that the plate and the anodearray have begun to contact one another. This measurement can also bedone optically, for instance with a laser, magnetic, or electricalsensor. Coplanarity of the anode array and the cathode is also extremelyimportant for the quality and consistency of deposition. Similar zeroingtechniques may be employed at multiple locations across the cathodeplane to ensure coplanarity, with adjustment in the anode holder,cathode holder or both.

The mechanical positioning system may move the anode array, the plate,or both. In the illustrative apparatus shown in FIG. 18 , actuators 224a may move the anode array 201, and actuators 224 b may move the plate1601. For example, actuators 224 b may affect the positioning of theclamps 1801 a/1802 a and 1801 b/1802 b in order to modify the positionor orientation of plate 1601. One or more embodiments may have only oneof actuators 224 a or 224 b; one or more embodiments may have both.Motion of the anode array may have as many as six degrees of freedom 225a, to allow the anode array to be placed into any desired position andorientation. Similarly motion of the plate may have as many as sixdegrees of freedom 225 b, to allow the plate to be placed into anydesired position and orientation. The actuators 224 a and 224 b may becontrolled by processor 222, which may obtain sensor data indicating therelative position and orientation of the anode array and the plate, andmay control actuators 224 a and 224 b to set this relative position andorientation to desired values.

In one or more embodiments, the plate 1601 may have a horizontal extentthat exceeds the size of anode array 201. In these situations, the anodearray may be shifted horizontally relative to the plate to successivelyconstruct interconnection structures in different subregions of theplate. For example, in FIG. 18 , a horizontal repositioning 1810 ofanode array 201 may be performed after features are constructed for thetiles on the right side of the plate.

One or more embodiments may also include a fluid system to manage theflow of and condition of electrolyte solution 210. For example, in FIG.18 the fluid system pumps fluid 1803 from the right side across the gapbetween the anode array and plate, and fluid exits at position 1804 forrecirculation. The fluid system may have for example any or all of apump, filter, temperature control system (temperature gauge, heater,chiller), tubing, analytical equipment such as pH and ion concentrationsensors (conductivity, spectrophotometer, mass spectrometer, inductivelycoupled plasma mass spectrometry, others), a leaching system to absorbundesired byproducts, and replenishment system designed to addelectrolyte bath components back to the bath as they are consumed. Allof these system components may be designed to withstand the corrosiveelectrodeposition environment. Fluid flow or motion of the systemcomponents may also be used to prevent or reduce bubbles that may formduring electrodeposition. A bubble clearing cycle may be initiatedperiodically or based on measurements that indicate reduced depositionefficiency, such as reductions in measured current overall or atindividual anodes that indicate lack of a conductive path or bubblesinsulating the anodes. One or more embodiments may use ultrasonicationof the fluid to better flush bubbles, pulsing flow rather than constantfluid flow rate. For example, an ultrasonic transducer may be placed incontact with some combination of the fluid, anode, and cathode; it mayinjects ultrasonic energy into the solution which causes gas bubbles inthe solution to release from their substrates and break into smallerbubbles, two aspects which make the bubbles easier to remove from theactive build area along with the flowing solution. One or moreembodiments may also vibrate the entire assembly to clear bubbles.

The fluid flows 1803 and 1804 shown in FIG. 18 are parallel to theplanes of the plate and the anode array. In one or more embodiments,fluid flow may be perpendicular to these planes, for example throughfluid supply holes in the anode array, cathode, or both; thisperpendicular flow may be more effective in some situations and it mayimprove bubble removal. One or more embodiments may incorporate featuressuch as ridges into the surface of the anode array that are aligned withthe fluid flow to improve flow and bubble removal.

In some embodiments, it may be possible to deposit multiple materialsonto the plate. For example, columns of one material may be extended bydepositing a different material on top of the first material. Oneexample of this would be a copper deposit capped with a solder material(tin or tin alloy for instance). These different materials may bedeposited by moving the substrate from one machine to another, eachequipped with a different material, or the process may for example useparallel fluid handling systems with independent components for eachtype of material when material incompatibility issues preclude the useof shared components for the materials. For instance, each material maybe housed in a separate tank and may have separate temperature control,filtration, pH management, etc. In addition, a fluid purge system may beutilized to flush the shared components (build chamber, electrode array)and between material swaps. This system could for example be a cleanwater supply that rinses the system to a collection vessel or drain. Insome embodiments, multiple build chambers may be employed, for exampleby moving the plate between build chambers.

A control system, which may include processor 222, may collect sensorinformation, and carry out the deposition of structures as dictated by abuild plan which is entered prior to deposition. The control system mayingest data from the electrolyte bath monitoring equipment, mechanicalpositioning sensors, and plating power systems. For example, voltage andcurrent may be measured at the system level (bulk) and/or at eachindividual anode, or at some subset of anodes.

This collected information may be used as part of an automated buildquality determination process. For example, this information may be usedto determine if a feature broke or failed to form properly during thebuild process and thus report manufacturing yield without a subsequentinspection step.

In a typical deposition cycle the control system may set current and/orvoltage of each anode element in accordance with the build plan,position the anode array relative to the plate, engage the pump to causesolution flow and measure the current, voltage, and deposition time bothat each individual anode and of the system as a whole. When certainthresholds are met, for instance a calculated charge (anode current overtime), or current/voltage spikes indicate a short circuit, the systemmay deactivate certain anodes and/or reposition the anode array relativeto the plate to continue the process. At certain points in the buildprocess the mechanical system may purposefully increase the gap tofacilitate greater fluid velocity, for example to enable clearing ofgenerated gas bubbles and/or refreshing the electrolyte in the activebuild area.

In another embodiment, an additional anode may be in fluid contact withthe plating cell which is used to sequentially deposit the bath materialonto the anode array. This modifies the surface of the anode array froman insoluble electrode material to a soluble one and can be beneficialto reducing secondary gas formation, the reduction of undesirablesecondary reactions, and/or increase the lifetime of the anodethemselves.

In some situations, when a plate is left sitting in the electrolytesolution, the deposit may be slowly etched by the plating bath,effectively undoing the deposition. To counteract this effect, one ormore embodiments may use any of several techniques to maintain acathodic potential on the cathode and avoid material loss. The firsttechnique may use a sacrificial zinc anode which is bonded electricallyto the cathode and is placed into the bath. The zinc component dissolvesinto solution more readily than a copper deposit and therefore protectsthe deposit. This may be incorporated with a secondary bath and saltbridge/ion membrane to avoid zinc ions contaminating the bath. Anothertechnique may use active cathode current protection. In this method, thepotential of the cathode may be maintained at a level slightly lowerthan the anodes and electrolyte to ensure that a constant but very smallforward current is always acting on the cathode.

Illustrative materials targeted for deposition are In, Cu, Sn, Ni, Co,Ag, Au, Pb, and alloys of these materials such as SnAg, NiCo. Additivesmay be used in the electrolyte chemistry to improve deposit qualitiessuch as surface finish, density, residual stresses, etc. For example, inone or more embodiments suppressing additives may be added to theelectrolyte. These additives may function to slow or stop depositionfrom occurring on the lower current density regions on the cathode. Thismay be useful because it may allow for a more distinct edge at the baseof the deposit. Without these suppressing additives, a more diffusededge may occur at the base of each deposit.

Though the process may eliminate the need for the photomasking steps onthe plate, a photomasking step may also be employed in one or moreembodiments to help improve the resolution and initial formation of thestructures.

One or more embodiments may deposit interconnection features onto aconductive seed layer that is placed onto the plate. An illustrative setof steps using the seed layer are shown in FIG. 19 . Step 1901 depositsan initial conductive seed layer 1601 a onto plate 1601. This step maybe performed using physical vapor deposition (“PVD”), for example. Inone or more embodiments, this initial seed layer 1601 a may be thinnerthan a normally deposited seed layer used in wafer plating applications.The layer may then be thickened in step 1902 using electrochemicaldeposition, by placing the plate and the seed layer into the electrolytesolution and plating the entire seed layer with material to thicken it,resulting in a thickened conductive seed layer 1601 b. Potentialbenefits of using a thin initial seed layer and then thickening it viaelectrodeposition may include reducing PVD tool usage for seed layerdeposition, having greater control over the thickness of the seed layer,being able to vary the thickness of the seed layer across the substrate,being able to achieve thicker seed layers than are feasibly deposited ina PVD process, and construction of multi-material seed layers. Step 1903then deposits interconnection features such as bump 1603 onto thethickened conductive seed layer 1601 b, as described above. Finally,step 1904 removes the seed layer between the interconnection structures,so that the individual interconnects are electrically isolated.

FIGS. 20A, 20B, and 20C show illustrative benefits of usingelectrodeposition to construct interconnection structures compared tothe existing art. FIG. 20A shows illustrative wafer bumps or pillarssuch as pillar 1603 a that may be constructed using electrodeposition orthe existing art, using for example a photoresist-based process. Threeimportant dimensions include the pillar diameter 2001, the pillar height2002, and the inter-pillar spacing 2003 (between centers). For typicalstate-of-the-art processing using photoresist, pillar diameter 2001 isapproximately 50 μm, pillar height 2002 is approximately 50 μm to 100μm, and pillar spacing 2003 is approximately 100 μm. FIG. 20B showsillustrative dimensions that may be achievable using one or moreembodiments of the invention for deposition of interconnectionstructures such as pillar 1603 b: pillar diameter 2011 may be below 10μm, pillar height 2012 may be 200 μm or more for a 10 μm diameter, andpillar spacing 2013 may be as low as 10 μm to 20 μm. These valuesrepresent substantial improvement over the existing art, with taller andsmaller diameter pillars that are spaced closer together. The pillaraspect ratio (height to diameter) achievable using one or moreembodiments of the invention may be greater than 10:1, which may beunachievable using photoresist-based processes due to limitations in howthickly the photoresist can be applied and exposed.

FIG. 20C shows another illustrative benefit of one or more embodimentsof the invention: interconnection structures may include shapes withdiagonal, slanted, or horizontal sections. Typical wafer bumps used inthe art rise perpendicularly to the surface of the semiconductor die.These vertical structures allow connection of die pads to connectionpoints directly across the location of the corresponding die padlocations. However, in some situations it may be advantageous to havenon-vertical interconnection features. Because of the flexibility of theelectrochemical additive manufacturing process, die pad connectingstructures are not limited to simple vertical columns. In someembodiments, horizontal structures can be fabricated to connect widelyseparated signals. This can be done for many reasons, includingcustomizing chips based on the same die, interconnecting widelyseparated signals not amenable to on-die interconnect, etc. For example,these techniques may be used to bring die signals out to the edge of thepackage for connection convenience. In some embodiments, one or morecolumns may be angled instead of being vertical to the die surface. Forexample, some or all of the columns may be angled in the same directionto horizontally offset the die from the resulting connection points. Insome embodiments, some columns may be angled away from each other(splayed out) to create connection points that are separated fartherapart than the pads on the die are separated. In the illustrativeexample shown in FIG. 20C, pillar 1603 c has a vertical section 2021connected to a largely horizontal section 2020; this geometry moves theconnection points to the edges of the plate. Non-vertical geometries mayalso be beneficial for heat sink structures, which may be constructed onplates instead of or in addition to interconnection structures. In someembodiments, heat sinks may be electrodeposited onto either or bothsides of an integrated circuit die, either in conjunction withinterconnect structure deposition or independently.

FIG. 21 shows illustrative techniques that may be used in one or moreembodiments to construct horizontal (or slanted, non-vertical) segmentsof interconnection features or heat sink features, such as those shownin FIG. 20C. Initially, step 2101 deposits vertical sections of thefeatures, such as sections 2110 a and 2111 a, onto plate 1601, which mayhave a conductive seed layer 1601 a. Horizontal sections 2110 b and 2111b may then be deposited using successive activation 2103 of selectedanodes to build the features horizontally parallel to the anode array.This process is described above for example with respect to FIG. 6 . Insome embodiments, an active anode (or anodes) is activated until acurrent short is observed. At that point, the currently active anode(s)are deactivated and then subsequent anodes are activated to continue thestructure.

Creating horizontal structures may introduce overhang effects,especially if the resulting structure is long and thin. When creatingsuch 3D interconnect structures, overhang effects may be amelioratedthrough many techniques, for example, techniques that reduce the stressexperienced by the overhanging structure. Performing the deposition in amicrogravity environment is one possible way to avoid the stress due togravity. Other techniques are also possible.

To reduce overhang stress in some embodiments, a multi-material buildcan be performed, with or without material removal between steps. Forexample, in one or more embodiments the manufacturing process may buildcolumns, pot (fill with inert material such as epoxy or the like) to thecolumn top, then build horizontal structures and more columns, potagain, build orthogonal horizontal structures, etc. This technique isshown in FIG. 21 as step 2102, which deposits inert material 2112 aroundthe vertical columns 2110 a and 2111 a. This inert material thenprovides support for the horizontal structures 2110 b and 2111 bconstructed in step 2103.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the scope of the invention set forth in the claims.

What is claimed is:
 1. A method of electrochemically additivemanufacturing an object using deposition-feedback control, the methodcomprising steps of: placing a surface of a cathode into an electrolytesolution; placing an anode array in contact with the electrolytesolution, wherein: the anode array comprises a plurality of depositionanodes; and each of the plurality of deposition anodes is configured toprovide an electric current that flows to the cathode through theelectrolyte solution, resulting in deposition of material onto thecathode; transmitting control signals to the anode array based on one ormore process parameter values of a build plan for a layer of the object;producing a deposition analysis by analyzing one or more feedbacksignals, generated by one or more sensors responsive to the depositionof the material onto the cathode; and performing one or more maintenanceactions on the anode array, when, based on the deposition analysis. 2.The method according to claim 1, wherein the one or more feedbacksignals constitute a map of current density across the anode array. 3.The method according to of claim 1, further comprising steps of:dividing a target map, associated with the layer, into regions, whereinsubsets of the plurality of deposition anodes are associated withdifferent ones of the regions; and alternately activating the subsets ofthe plurality of deposition anodes.
 4. The method according to of claim1, wherein the step of producing the deposition comprises, for at leastone of the plurality of deposition anodes, determining one or more of:an electric potential difference relative to the cathode; an electriccurrent through the electrolyte solution to the cathode; or a period ofactivation.
 5. The method according to of claim 1, further comprisingremoving bubbles from the electrolyte solution by vibrating at least oneof the electrolyte, the cathode, or the anode array.
 6. The methodaccording to of claim 1, wherein the one or more sensors comprise atleast one of an electric-current sensor, a position sensor, or anoptical imager.
 7. The method according to claim 1, wherein the step ofperforming the one or more maintenance actions on the anode arraycomprises a step of depositing replacement material onto at least one ofthe plurality of deposition anodes to replace lost material that haseroded from at least the one of the plurality of deposition anodes. 8.The method according to claim 7, wherein the step of depositing thereplacement material onto at least the one of the plurality ofdeposition anodes to replace the lost material that has eroded from atleast the one of the plurality of deposition anodes comprises reversingdirection of the electric current so that at least the one of theplurality of deposition anodes acts as a cathode, and the electriccurrent flows from a secondary anode to at least the one of theplurality of deposition anodes, acting as the cathode.
 9. The methodaccording to claim 8, wherein the secondary anode is a bulk anode thatis larger than at least the one of the plurality of deposition anodes.10. The method according to claim 8, wherein the secondary anode is madeof an inert material.
 11. The method according to claim 10, wherein theinert material comprises platinum.
 12. The method according to claim 8,wherein the secondary anode is composed of a material that is identicalin composition to the material, deposited onto the cathode.
 13. Themethod according to claim 7, further comprising transmitting controlsignals to the anode array based on one or more process parameter valuesof a build plan for a subsequent layer of the object, so that anelectric potential difference, created between at least the one of theplurality of deposition anodes and the cathode, is such that only thereplacement material, deposited onto at least the one of the pluralityof deposition anodes to replace the lost material that has eroded fromat least the one of the plurality of deposition anodes, is dissolvedinto the electrolytic solution when the electric current flows from atleast the one of the plurality of deposition anodes to the cathodethrough the electrolyte solution, resulting in deposition of thematerial onto the cathode.
 14. The method according to claim 7, whereinthe replacement material, deposited onto at least the one of theplurality of deposition anodes, is more soluble than the lost material,eroded from at least the one of the plurality of deposition anodes. 15.The method according to claim 1, wherein the step of performing the oneor more maintenance actions on the anode array comprises a step ofactivating two adjacent ones of the plurality of deposition anodes, ontowhich a film has formed that bridges a gap between at the two adjacentones of the plurality of deposition anodes, so that the film is removed.16. The method according to claim 15, wherein the step of activating thetwo adjacent ones of the plurality of deposition anodes, onto which thefilm has formed that bridges the gap between the two adjacent ones ofthe plurality of deposition anodes, comprises moving the cathode awayfrom the plurality of deposition anodes and activating only the twoadjacent ones of the plurality of deposition anodes, onto which the filmhas formed.
 17. The method according to claim 15, wherein the step ofactivating the two adjacent ones of the plurality of deposition anodes,onto which the film has formed that bridges the gap between the twoadjacent ones of the plurality of deposition anodes, is performed whenan electric current, passing through each of the two or more adjacentones of the plurality of deposition anodes, is higher than an electriccurrent, passing through any other one of the plurality of depositionanodes.
 18. The method according to claim 7, wherein the step ofperforming the one or more maintenance actions on the anode arrayfurther comprises a step of activating two of the plurality ofdeposition anodes, onto which a film has formed that bridges a gapbetween the two of the plurality of deposition anodes, so that the filmis removed.
 19. The method according to claim 7, further comprisingremoving bubbles from the electrolyte solution by vibrating at least oneof the electrolyte, the cathode, or the anode array.
 20. The methodaccording to claim 7, further comprising steps of: dividing a targetmap, associated with the layer, into regions, wherein subsets of theplurality of deposition anodes are associated with different ones of theregions; and alternately activating the subsets of the plurality ofdeposition anodes.